AmericaOnline, or AOL as they are usually called, are a rather big ISP, famous for their free coasters.
Footnote: There are various kinds of coasters?. Roller coasters are the more popular kind. Also, useless CDs, such as one that wasn't written properly by your CD writer, or an AmericaOnline sign-up CD, are often used as coasters.
One page links to AmericaOnline:
